Weird shadows in render view only
Your model is huge, and that is causing lots of problems.

Specifically for those shadows Ambient Occlusion is to blame. The model is so huge that even with the insane values you have for ambient occlusion, it only affects small creases in the model, but with great intensity. If you disable ambient occlusion however you get another issue: everything is dark.

The way you have set up your background node does not affect your model, so no environment light exists. You could either remove the camera ray constraint from the world texture, use a nice neutral grey for background and use the compositor to set up a background color, or keep it and add some lights to your scene.

However adding lights does nothing, unless you crank up the intensity to hundreds of thousands, another issue with the size of your model.

I'd say just resize your model to a more manageable size (something like a real human): then both AO and lights will work as expected with sane values.